Liquid crystal display devices (hereinafter, also referred to as LCDs) have become very popular because they can be designed as light, thin, less power-consuming display devices. They are used in applications, essential for our daily life and business, including mobiles, various monitors, and large-scale televisions. LCDs are still under development to provide a wider viewing angle and improved contrast, that is, to further improve display quality, and to provide one having more functions.
Current LCDs are configured to produce images by controlling the alignment of liquid crystal molecules in response to an electric field applied thereto in such a manner to change the polarization of light passing through the liquid crystal layer, thereby adjusting the amount of light passing through a polarizer.
The display quality of LCDs depends on the alignment of liquid crystal molecules to which a voltage is being applied, and the magnitude and direction of an electric field applied thereto. Various display modes of LCDs are categorized based on the alignment of liquid crystal molecules to which no voltage is being applied, and the electric field direction.
For example, a TN (Twisted Nematic) mode is a mode of liquid crystal elements in which liquid crystal molecules are twisted. Liquid crystal display devices of this mode can be driven by a low voltage and produced at low cost. Another example is a vertical electric field mode which is a mode of liquid crystal elements in which the liquid crystal alignment is vertical to substrates when no voltage is applied, and is called “VA (Vertical Alignment) mode”. The VA mode is a mode advantageous in terms of high contrast, and is used in growing applications. Various techniques have been developed to satisfy all of desired features including a wide viewing angle, high contrast, and high-speed response in these modes. One notable example of current important techniques in this field is an alignment division technique to divide each pixel into regions such that liquid crystal molecules within each pixel are aligned in different directions. This technique improves display quality. In particular, an MVA (Multi-Domain Vertical Alignment) mode which can provide an excellent wide viewing angle due to its alignment division pattern described above is attracting attention.
One example of a VA mode with a conventional alignment division pattern is a VA mode (hereinafter, also referred to as VATN (Vertical Alignment Twisted Nematic) mode) in which two substrates are respectively provided with vertical alignment films for alignment control in directions perpendicular to each other so that liquid crystal molecules are twisted. One example thereof that has been disclosed so far is a liquid crystal electric optical device which is provided with a pair of substrates on the both side of a liquid crystal layer made of a negative dielectric anisotropy liquid crystal material which becomes a nematic layer at least in a predetermined temperature range, and further provided, on the surfaces of the substrates facing the liquid crystal layer, with alignment films which align liquid crystal molecules substantially vertically to the substrate surfaces when no voltage is applied, wherein each of the alignment films on the substrates is divided into two or more alignment regions in each of which the liquid crystal molecules are slightly tilted in a different pretilt direction from the direction perpendicular to the substrate surfaces, and the substrates are assembled together such that the boundary between the alignment regions of one of the substrates runs across the boundary between the alignment regions of the other substrate (see, for example, Patent Literature 1).
In addition to the example of the VA mode, there have been proposed liquid crystal display devices of a common TN mode with an alignment division pattern in which liquid crystal molecules are aligned horizontal when no voltage is applied. One example thereof which has been disclosed so far is a multi-pixel liquid crystal display device comprising two facing substrates each provided with an electrode and a liquid crystal alignment film, and a nematic liquid crystal therebetween, wherein pixels are arranged as a matrix and each are divided into regions which differ in visual angle direction of liquid crystal molecules such that the visual angle directions of lower regions of pixels in any row are the same as the visual angle directions of upper regions of pixels in the next row, and the visual angle directions of lower regions of pixels in any column are the same as the visual angle directions of lower regions of pixels in the next column (see, for example, Patent Literature 2).
Additionally, methods for producing liquid crystal display devices with such conventional alignment division patterns have also been proposed such as a method for producing a liquid crystal display device comprising a first substrate, a second substrate facing the first substrate, a liquid crystal layer between the substrates, a first alignment film provided on the liquid crystal layer side surface of the first substrate, and a second alignment film provided on the liquid crystal layer side surface of the second substrate, wherein the production method comprises subjecting the first alignment film and/or the second alignment film to scanning exposure continuously over a plurality of pixels, the scanning exposure comprising exposing the first alignment film and/or the second alignment film while scanning an inside of each pixel more than one time in antiparallel directions to form, in the each pixel region, regions in which liquid crystal molecules are aligned in antiparallel directions to the surface (s) of the first alignment film and/or the second alignment film (see, for example, Patent Literature 3).